Ferroelectric film, method of manufacturing the same, ferroelectric memory and piezoelectric device

ABSTRACT

A ferroelectric film wherein 5 to 40 mol % in total of at least one of Nb, V, and W is included in the B site of a Pb(Zr,Ti)O 3  ferroelectric which includes at least four-fold coordinated Si 4+  or Ge 4+  in the A site ion of a ferroelectric perovskite material in an amount of 1% or more. This enables to significantly improve reliability of the ferroelectric film.

This is a Division of application Ser. No. 10/807,427 filed Mar. 24,2004. The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

Japanese Patent Application No. 2003-91523, filed on Mar. 28, 2003,Japanese Patent Application No. 2003-209116, filed on Aug. 27, 2003, andJapanese Patent Application No. 2004-5297, filed on Jan. 13, 2004 arehereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a ferroelectric memory and apiezoelectric device formed by using a ferroelectric capacitor. Thepresent invention also relates to a ferroelectric film which can be usedin common for 1T1C and 2T2C type ferroelectric memory devices whichinclude a ferroelectric capacitor and a select cell transistor, a simplematrix type ferroelectric memory device in which a memory cell is formedby using only a ferroelectric capacitor without a cell transistor, and a1T type ferroelectric memory device in which a ferroelectric film isused as a gate oxide film, a method of manufacturing the ferroelectricfilm, a ferroelectric memory, and a piezoelectric device.

In recent years, research and development of a film such as PZT or SBT,a ferroelectric capacitor using the film, and a ferroelectric memorydevice have been extensively conducted. The structure of a ferroelectricmemory device is roughly divided into 1T, 1T1C, 2T2C, and simple matrix.Since the 1T type ferroelectric memory device has a structure in whichretention (data retention) is as short as one month due to occurrence ofan internal electric field in the capacitor, it is impossible to securea 10-year guarantee generally required for semiconductors. The 1T1C and2T2C type ferroelectric memory devices have almost the sameconfiguration as that of a DRAM, and include a select transistor.Therefore, a DRAM manufacturing technology can be utilized and a writespeed approximately equal to the write speed of an SRAM can be realized.Therefore, small capacity products with a capacity of 256 kbits or lesshave been produced on a commercial basis.

As a ferroelectric material used for a ferroelectric memory, aperovskite material such as Pb(Zr,Ti)O₃ (PZT) and aBi-layered-structured ferroelectric such as Bi₄Ti₃O₁₂ (BIT) have beenused. However, since these materials have a leakage current density ofabout 10⁻⁴ to 10⁻⁶ A/cm², an extremely large current leakage occurs.

PZT is used as a typical ferroelectric material. A material having acomposition in or near the mixed region of the rhombohedral crystal andthe tetragonal crystal, in which the Zr/Ti ratio is 52/48 or 40/60, isused as PZT. PZT is used after doping with an element such as La, Sr, orCa. The above region is used to secure reliability, which is the mostimportant requirement for the memory device. Although the hysteresisshape is excellent in the Ti-rich tetragonal region, a Schottky defectoccurs due to the ionic crystal structure, whereby a failure in leakagecurrent characteristics or imprint characteristics (degree of change inhysteresis shape) occurs. This makes it difficult to secure reliability.

In recent years, it is known that the crystallization temperature isreduced by adding Si and Ge to the constituent elements of theferroelectric crystal in order to solve the above-described problems.However, it is not known which site Si and Ge replace in the crystal.This is an important subject in the functional design of theferroelectric material in the case of introducing an element other thanSi and Ge.

The simple matrix type ferroelectric memory device has a cell sizesmaller than that of the 1T1C and 2T2C type ferroelectric memorydevices, and allows the capacitors to be multilayered. Therefore, anincrease in the degree of integration and a reduction of cost areexpected by using the simple matrix type ferroelectric memory device. Aconventional simple matrix type ferroelectric memory device is disclosedin Japanese Patent Application Laid-open No. 9-116107, for example.Japanese Patent Application Laid-open No. 9-116107 discloses a drivemethod in which a voltage of one-third the write voltage is applied tounselected memory cells when writing data into the memory cell.

However, this technology does not describe the hysteresis loop of theferroelectric capacitor necessary for the operation in detail. Thepresent inventors have developed a ferroelectric memory device and foundthat a hysteresis loop with excellent squareness is indispensable forobtaining a simple matrix type ferroelectric memory device which can beoperated in practice. As a ferroelectric material which can deal withsuch a requirement, Ti-rich tetragonal PZT may be employed. However, themost important subject is to secure reliability in the same manner asthe above-described 1T1C and 2T2C type ferroelectric memories.

BRIEF SUMMARY OF THE INVENTION

The present invention may provide a ferroelectric film which can beapplied to a ferroelectric capacitor having hysteresis characteristicscapable of being used for 1T1C, 2T2C, and simple matrix typeferroelectric memories, and a method of manufacturing such aferroelectric film. The present invention may further provide 1T1C,2T2C, and simple matrix type ferroelectric memories using the aboveferroelectric film, and a piezoelectric device.

According to one aspect of the present invention, there is provided aferroelectric film including a perovskite ferroelectric or a bismuthlayer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number), wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺is included in the A site ion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 are graphs showing inverse photoemission spectra determined byfirst-principles calculation when an ABO₃ perovskite structure has Si inthe A site (that is SiTiO₃) and when an ABO₃ perovskite structure has Siin the B site (that is PbSiO₃).

FIG. 2 is a graph showing XRD patterns of PZT and PZT+Si ferroelectricfilms deposited at 600° C.

FIG. 3 are graphs showing D-E hysteresis characteristics of PZT andPZT+Si ferroelectric films with a thickness of 100 nm which aredeposited at 600° C.

FIGS. 4A and 4B show Raman spectra of a PZT+Si film.

FIG. 5 shows a deposition flow using a sol-gel method.

FIG. 6 are graphs showing hysteresis characteristics obtained by using asol-gel solution for forming a ferroelectric film to which 1 mol % ofPbSiO₃ silicate and methyl succinate are added while changing the amountpf Nb added to the solution to 0, 5, 10, 20, 30 and 40 mol %.

FIG. 7 are graphs for comparison of X-ray diffraction patterns when theamount of Nb added is 20 mol % or more.

FIG. 8 is a graph showing Raman spectra of a PZTN film.

FIG. 9 is a graph showing conditions for PZTN to be an insulator.

FIG. 10 is a diagram showing a crystal structure of WO₃.

FIG. 11 shows XRD patterns when the amount of Si added to the A site ischanged to 5, 10, and 15 mol %.

FIG. 12 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 13 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 14 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 15 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 16 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 17 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 18 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 19 shows a ferroelectric memory according to one embodiment of thepresent invention.

FIG. 20 is an exploded perspective view of a recording head according toone embodiment of the present invention.

FIG. 21A is a plan view of a recording head according to one embodimentof the present invention; and FIG. 21B is a cross-sectional view of arecording head according to one embodiment of the present invention.

FIG. 22 is a schematic cross-sectional view showing a piezoelectricdevice according to one embodiment of the present invention.

FIG. 23 schematically showing a recording device according to oneembodiment of the present invention.

FIG. 24 is a flowchart showing steps of forming a ferroelectric filmaccording to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) According to a first embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion.

(2) According to a second embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion; and

wherein the ferroelectric film is a solid solution with a dielectricshown by X₂SiO₅, X₄Si₃O₁₂, X₂GeO₅ or X₄Ge₃O₁₂ (wherein X representsBi³⁺, Fe³⁺, Sc³⁺, Y³⁺, La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺,Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺ or Lu³⁺).

(3) According to a third embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻, (wherein A represents at least oneion selected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺,Sr²⁺, Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected fromthe group consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, andm is a natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion; and

wherein the ferroelectric film includes at least one transition elementin an amount of 5 to 40 mol % in total, the transition element havingthe maximum positive valence which is +1 or more greater than thevalence of the A site ion of the ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻.

(4) According to a fourth embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion; and

wherein the ferroelectric film includes at least one transition elementin an amount of 5 to 40 mol % in total, the transition element havingthe maximum positive valence which is +1 or more greater than thevalence of the B site ion of the ABO₃ or (Bi₂O₂)²⁺(A³⁻¹B_(m)O_(3m+1))²⁻.

(5) According to a fifth embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion;

wherein the ferroelectric film includes at least one transition elementhaving the maximum positive valence which is +1 or more greater than thevalence of the B site ion of the ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻;

wherein the ferroelectric film includes at least one transition elementhaving the maximum positive valence which is +1 or more greater than thevalence of the A site ion of the ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻; and

wherein the transition elements are included in an amount of 5 to 40 mol% in the A and B sites in total.

(6) According to a sixth embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion;

wherein the ferroelectric film is a solid solution with a dielectricshown by X₂SiO₅, X₄Si₃O₁₂, X₂GeO₅ or X₄Ge₃O₁₂ (wherein X representsBi³⁺, Fe³⁺, Sc³⁺, Y³⁺, La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺,Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Y³⁺ or Lu³⁺); and

wherein the ferroelectric film includes at least one transition elementin an amount of 5 to 40 mol % in total, the transition element havingthe maximum positive valence which is +1 or more greater than thevalence of the A site ion of the ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻.

(7) According to a seventh embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion;

wherein the ferroelectric film is a solid solution with a dielectricshown by X₂SiO₅, X₄Si₃O₁₂, X₂GeO₅ or X₄Ge₃O₁₂ (wherein X representsBi³⁺, Fe³⁺, Sc³⁺, Y³⁺, La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺,Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺ or Lu³⁺); and

wherein the ferroelectric film includes at least one transition elementin an amount of 5 to 40 mol % in total, the transition element havingthe maximum positive valence which is +1 or more greater than thevalence of the B site ion of the ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻.

(8) According to an eighth embodiment of the present invention, there isprovided a ferroelectric film including a perovskite ferroelectric or abismuth layer-structured ferroelectric shown by ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ (wherein A represents at least one ionselected from the group consisting of Li⁺, Na⁺, K⁺, Pb²⁺, Ca²⁺, Sr²⁺,Ba²⁺, Bi³⁺ and La³⁺, B represents at least one ion selected from thegroup consisting of Fe³⁺, Ti⁴⁺, Zr⁴⁺, Nb⁵⁺, Ta⁵⁺, W⁶⁺ and Mo⁶⁺, and m isa natural number),

wherein at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ is included in the Asite ion;

wherein the ferroelectric film is a solid solution with a dielectricshown by X₂SiO₅, X₄Si₃O₁₂, X₂GeO₅ or X₄Ge₃O₁₂ (wherein X representsBi³⁺, Fe³⁺, Sc³⁺, Y³⁺, La³⁺Ce³⁺, Pr³⁺, Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺,Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺ or Lu³⁺);

wherein the ferroelectric film includes at least one transition elementhaving the maximum positive valence which is +1 or more greater than thevalence of the B site ion of the ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²;

wherein the ferroelectric film includes at least one transition elementhaving the maximum positive valence which is +1 or more greater than thevalence of the A site ion of the ABO₃ or(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻; and

wherein the transition elements are included in an amount of 5 to 40 mol% in the A and B sites in total.

(9) Any of the above ferroelectric films may include Pb(Zr, Ti)O₃ whichincludes at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the A site ionin an amount of 1% or more; and at least one transition element havingthe maximum positive valence of +3 or more may be included in the A sitein an amount of 5 to 40 mol % in total.

(10) Any of the above ferroelectric films may include Pb(Zr, Ti)O₃ whichincludes at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the A site ionin an amount of 1% or more; and at least one transition element havingthe maximum positive valence of +5 or more may be included in the B sitein an amount of 5 to 40 mol % in total.

(11) According to a ninth aspect of the present invention, there isprovided a ferroelectric film including Pb(Zr, Ti)O₃ which includes atleast four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amountof 1% or more, wherein at least one transition element having themaximum positive valence of +3 or more is included in the Pb site;

wherein at least one transition element having the maximum positivevalence of +5 or more is included in the Zr or Ti site; and

wherein the transition elements are included in an mount of 5 to 40 mol% in the Pb and Zr or Ti sites in total.

(12) According to a tenth embodiment of the present invention, there isprovided a ferroelectric film including Pb(Zr, Ti)O₃ which includes atleast four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amountof 1% or more,

wherein at least one of La and other lanthanoid series ions is includedin the Pb site in an amount of 5 to 40 mol % in total.

(13) According to an eleventh aspect of the present invention, there isprovided a ferroelectric film including Pb(Zr, Ti)O₃ which includes atleast four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amountof 1% or more,

wherein at least one of Nb, V and W is included in the Zr or Ti site inan amount of 5 to 40 mol % in total.

(14) According to a twelfth embodiment of the present invention, thereis provided a ferroelectric film including Pb(Zr, Ti)O₃ which includesat least four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in anamount of 1% or more,

wherein at least one of La and other lanthanoid series ions is includedin the Pb site, and at least one of Nb, V and W is included in the Zr orTi site, in an amount of 5 to 40 mol % in the Pb and Zr or Ti sites intotal.

(15) Any of the above ferroelectric films may further include at leastone of Nb, V and W in the Zr or Ti site in an amount twice the amount ofPb ion vacancy in the Pb site.

(16) Any of the above ferroelectric films may be included (111)-orientedtetragonal crystals.

(17) Any of the above ferroelectric film may be included (001)-orientedrhombohedral crystals.

(18) According to a thirteenth embodiment of the present invention,there is provided a method of manufacturing a ferroelectric filmsincluding Pb(Zr,Ti)O₃, the method comprising:

using a sol-gel solution for forming Pb(Zr,Ti)O₃ which includes at leastfour-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amount of 1%or more.

(19) According to a fourteenth embodiment of the present invention,there is provided a method of manufacturing a ferroelectric filmsincluding Pb(Zr,Ti)O₃, the method comprising:

using a sol-gel solution for forming Pb(Zr,Ti)O₃ which includes at leastfour-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amount of 1%or more,

wherein a mixed solution prepared by mixing a sol-gel solution forforming PbZrO₃ which includes at least four-fold coordinated Si⁴⁺ orGe⁴⁺ in the Pb site ion in an amount of 1% or more with a sol-gelsolution for forming PbTiO₃ which includes at least four-foldcoordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amount of 1% or moreis used as the sol-gel solution for forming Pb(Zr,Ti)O₃.

(20) According to a fifteenth embodiment of the present invention, thereis provided a method of manufacturing a ferroelectric films includingPb(Zr,Ti)O₃, the method comprising:

using a sol-gel solution for forming Pb(Zr,Ti)O₃ in which the amount ofPb ranges from 90 to 120% of the stoichiometric composition ofPb(Zr,Ti)O₃.

(21) Any of the above ferroelectric films may include Bi₄Ti₃O₁₂including at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the A site ionin an amount of 1% or more; and at least one transition element havingthe maximum positive valence of +4 or more may be included in the A sitein an amount of 5 to 40 mol % in total.

(22) Any of the above ferroelectric films may include Bi₄Ti₃O₁₂including at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the A site ionin an amount of 1% or more; and at least one transition element havingthe maximum positive valence of +5 or more may be included in the B sitein an amount of 5 to 40 mol % in total.

(23) According to a sixteenth embodiment of the present invention, thereis provided a ferroelectric film including Bi₄Ti₃O₁₂ which includes atleast four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Bi site ion in an amountof 1% or more,

wherein at least one transition element having the maximum positivevalence of +4 or more is included in the Bi site;

wherein at least one transition element having the maximum positivevalence of +5 or more is included in the Ti site; and

wherein the transition elements are included in an amount of 5 to 40 mol% in the Bi and Ti sites in total.

(24) According to a seventeenth embodiment of the present invention,there is provided a ferroelectric film including Bi₄Ti₃O₁₂ whichincludes at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Bi site ionin an amount of 1% or more,

wherein at least one of Nb, V and W is included in the Ti site in anamount of 5 to 40 mol % in total.

(25) Any of the above ferroelectric films may further include at leastone of Nb, V, and W in the Ti site in an amount twice the amount of Biion vacancy in the Bi site.

(26) Any of the above ferroelectric films may be included (111), (110),and (117) oriented orthorhombic crystals.

(27) According to an eighteenth embodiment of the present invention,there is provided a method of manufacturing a ferroelectric filmsincluding Bi₄Ti₃O₁₂, the method comprising:

using a sol-gel solution for forming Bi₄Ti₃O₁₂ which includes at leastfour-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Bi site ion in an amount of 1%or more.

(28) According to a nineteenth embodiment of the present invention,there is provided a method of manufacturing a ferroelectric filmsincluding Bi₄Ti₃O₁₂, the method comprising:

using a mixed solution prepared by mixing a solution prepared by mixinga sol-gel solution for forming Bi₂O₃ with a sol-gel solution for formingTiO₂ at a molar ratio of 2:3 with a sol-gel solution for forming adielectric shown by X₂SiO₅, X₄Si₃O₁₂, X₂GeO₅, or X₄Ge₃O₁₂ (wherein Xrepresents Bi³⁺, Fe³⁺, Sc³⁺, Y³⁺, La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Pm³⁺, Sm³⁺,Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺, or Lu³⁺) so that Si⁴⁺ orGe⁴⁺ is included in an amount of 1 mol % or more.

(29) According to a twentieth embodiment of the present invention, thereis provided a method of manufacturing a ferroelectric films includingBi₄Ti₃O₁₂, the method comprising:

using a sol-gel solution for forming Bi₄Ti₃O₁₂ in which an excess amountof Bi ranges from 90 to 120% of the stoichiometric composition ofBi₄Ti₃O₁₂.

(30) According to a twenty-first embodiment of the present invention,there is provided a ferroelectric memory comprising any of the aboveferroelectric films.

(31) According to a twenty-second embodiment of the present invention,there is provided a piezoelectric device comprising any of the aboveferroelectric films.

The embodiments of the present invention are described below in detailwith reference to the drawings.

1. Simulation Result for Site Substitution Effect

In the case of applying a ferroelectric material to a memory, it isknown that the B site ion of a ferroelectric material having aperovskite structure or a bismuth layered structure is replaced by Si orGe in order to reduce the crystallization temperature of theferroelectric material and improve fatigue characteristics. However,since Si or Ge has a very small ionic radius, Si or Ge can replace the Bsite under an extremely high-pressure environment at a pressure higherthan 50 atmospheres.

FIG. 1 shows inverse photoemission spectra determined byfirst-principles calculation when an ABO₃ perovskite structure has Si inthe A site (that is SiTiO₃) and when an ABO₃ perovskite structure has Siin the B site (that is PbSiO₃).

The bandgap of PbSiO₃, in which Si is assumed to be in the B site, isreduced in an amount of 1.57 eV (becomes semiconductive) in comparisonwith SiTiO₃ in which Si is in the A site, and becomes leaky. A gentlysloped spectrum edge is obtained when Si is in the B site, and a sharpspectrum edge is obtained when Si is in the A site. Specifically, higherinsulating properties are obtained when Si is in the A site.

In the case where Si is in the B site, the Si-2p peak appears at aposition 18.5 meV shallower than that in the case where Si is in the Asite. However, it was found that a further separation observation isdifficult and the site of Si cannot be distinguished by using ananalytical method such as XPS.

2. Ferroelectric Film

A 100 nm Pt coated Si substrate was used as a substrate. A film with athickness of 100 nm was formed by using a mixed sol-gel solutionprepared by adding a sol-gel solution for forming PbSiO₃ to a sol-gelsolution containing PbZr_(0.32)Ti_(0.68)O₃ ferroelectric material sothat the amount of Si was 10 mol % for one mol of PZT under depositionconditions as shown in FIG. 24. A PbZr_(0.32)Ti_(0.68)O₃ ferroelectricfilm with a thickness of 100 nm to which PbSiO₃ was not added was formedfor comparison.

FIG. 2 shows XRD patterns obtained by depositing the films at acrystallization temperature of 600° C. as shown in FIG. 24. The PZT andPZT+Si ferroelectric materials of the present embodiment exhibitedexcellent crystallinity. In the XRD patterns shown in FIG. 2, no changein the (111) peak position was observed.

A Pt upper electrode was formed. The ferroelectric characteristics ofthe PZT and PZT+Si ferroelectric films with a thickness of 100 nm wereevaluated using the upper Pt electrode and the lower Pt electrode. As aresult, the PZT and PZT+Si films of the present embodiment showed anexcellent ferroelectric hysteresis. FIG. 3 shows the D-E hysteresischaracteristics. The PZT+Si film of the present embodiment showedhysteresis characteristics similar to the hysteresis characteristics ofthe PZT film. However, the PZT+Si film of the present embodiment showedbetter leakage characteristics in comparison with the PZT film.

The fact that the PZT+Si film showed excellent hysteresischaracteristics suggests that Si was in the PZT crystal as theconstituent element of the crystal. The fact that shift of the XRD peakand a change in characteristics are not observed suggests that Sireplaced the A site of PZT. This is because the ferroelectriccharacteristics would change to a large extent if Si replaced the Bsite.

FIGS. 4A and 4B show Raman spectra of the PZT+Si film. FIG. 4A shows avibrational mode E(1TO) of the A site ion, and FIG. 4B shows avibrational mode A1(2TO) of the B site ion. As shown in FIG. 4A, changesin the vibrational mode E(1TO) of the A site ion were observed. As shownin FIG. 4B, changes in the vibrational mode A1(2TO) of the B site ionwere not observed. Therefore, it was confirmed that Si replaced the Asite.

In the present embodiment, ferroelectric characteristics of PZTN werecompared while changing the amount of Nb added to 0, 5, 10, 20, 30, and40 mol %. PbSiO₃ silicate was added to all specimens in an amount of 1mol %. The pH of the sol-gel solution for forming a ferroelectric filmwas adjusted to 6.0 by adding methyl succinate. A deposition flow shownin FIG. 5 was used. FIG. 6 shows the resulting hysteresischaracteristics.

In the case where the amount of Nb added was zero, a leaky hysteresiswas obtained. In the case where the amount of Nb added was 5 mol % ormore, excellent hysteresis characteristics with high insulatingproperties were obtained. In the case where the amount of Nb added was10 mol % or less, a change in ferroelectric characteristics was notobserved or observed only to a small extent. A change in ferroelectriccharacteristics was not observed in the case where the amount of Nbadded was zero, although the hysteresis was leaky. However, thehysteresis characteristics changed to a large extent in the case wherethe amount of Nb added was 20 mol % or more.

FIG. 7 shows comparison results of X-ray diffraction patterns. In thecase where the amount of Nb added was 5 mol %, the (111) peak positionis the same as that in the case where the amount of Nb added was zero.The (111) peak was shifted to the low angle side as the amount of Nbadded was increased to 20 mol % and 40 mol %. Specifically, the actualcrystal was rhombohedral although the composition of PZT was in theTi-Rich tetragonal region. The ferroelectric characteristics changed asthe crystal system changed. Therefore, it was found that theferroelectric characteristics are changed to a large extent by replacingthe B site ion, since the B site ion influences the ferroelectriccharacteristics to a large extent.

FIG. 8 shows Raman spectra of the PZTN film. As shown in FIG. 8, a largechange was observed in the vibrational mode A1(2TO) of the B site ion asthe amount of Nb added was increased. Taking the results in FIGS. 4A and4B into consideration, it was confirmed that Si replaces the A site andhas a function of causing Nb to be dissolved in the B site at lowtemperature.

In the case where Nb was added in an amount of 45 mol %, ferroelectriccharacteristics could not be confirmed due to the absence of hysteresis.However, it was found that the resulting film can be used as a highdielectric film due to a high dielectric constant.

The PZTN film of the present embodiment has very high insulatingproperties as described above. FIG. 9 shows conditions necessary forPZTN to be an insulator. Specifically, the PZTN film of the presentembodiment has very high insulating properties, and Nb is added in halfthe amount of Pb vacancy. As is clear from WO₃ shown in FIG. 10, theperovskite crystal can be formed even if the A site ion is deficient ata percentage of 100%. It is known that the crystal system of WO₃ easilychanges. Therefore, the amount of Pb vacancy in PZTN is positivelycontrolled and the crystal system is also controlled by adding Nb.

The same effect as described above can be obtained by adding Ta, W, V,or Mo to the PZTN film of the present embodiment as an additivesubstance instead of Nb. The effect similar to that of Nb can beobtained by using Mn as an additive substance. From the same viewpoint,Pb may be replaced by an element with a valence of +3 or more in orderto prevent Pb from being absent. As examples of such elements,lanthanoid series elements such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb and Lu can be given. As an additive for promotingcrystallization, a germanate may be used instead of a silicate.

This suggests that the PZTN film of the present embodiment is veryeffective in piezoelectric applications. In the case of using PZT inpiezoelectric applications, a Zr-rich rhombohedral region is generallyused. Zr-rich PZT is called soft PZT. This means that the crystal of thesoft PZT is soft. The soft PZT is used as an ink-jet nozzle of anink-jet printer. However, since the soft PZT is too soft, ink havinghigh viscosity cannot be jetted since the pressure of the ink is toohigh.

Ti-rich tetragonal PZT is called hard PZT. This means that the hard PZTis hard and brittle. However, in the present invention, the crystalsystem of the hard PZT can be artificially changed to the rhombohedralsystem. Moreover, the crystal system can be arbitrarily changed by theamount of Nb added. Furthermore, since Ti-rich PZT has a small relativedielectric constant, the hard PZT can be driven at low voltage.

This enables the hard PZT to be used as an ink-jet nozzle of an ink-jetprinter, for which the hard PZT has not been used. Moreover, since Nbprovides PZT with softness, PZT which is moderately hard but is notbrittle can be provided.

As described above, the present embodiment is not realized merely by theaddition of Nb. The present embodiment is realized by adding a silicatein addition to Nb. This also enables the crystallization temperature tobe reduced.

PbSiO₃ silicate was added to the PZTN film formed in the presentembodiment, in which the amount of Nb added was 40 mol %, in an amountof 5, 10, and 15 mol %. In the PZTN film in which the amount of Nb was40 mol %, PZT, which should be a tetragonal system, changed to arhombohedral system.

FIG. 11 shows XRD patterns when the amount of Si added to the A site ischanged to 5, 10, and 15 mol %. As shown in FIG. 11, PZT returned to theoriginal tetragonal system from the rhombohedral system as the amount ofSi added was increased. Specifically, since Si is small, Si can easilyenter the A site. The A site has 12 bonds. Si has a coordination numberof four and has four bonds. The perovskite is formed as a crystal evenif the A site is absent as described above. Therefore, it is easy tocause Si to bond to four of the 12 bonds.

Si which had entered the A site prevented inclination of the position ofthe oxygen octahedron which is the source of ferroelectricity, wherebythe crystal system returned to the original tetragonal system from therhombohedral system.

In the case where Si was added in an amount of 15% or more, the filmbecame a high dielectric having no hysteresis while maintaining arelative dielectric constant of 600. The relative dielectric constantshould be decreased unless Si becomes a part of the constituent elementsof the crystal structure. The relative dielectric constant is decreasedtogether with the remanent polarization, even if Si becomes the B siteion. In the case where Si becomes the A site ion, it is difficult forthe oxygen octahedron to move due to strong covalent bonding propertiesof Si, although the A site ion originally has strong ionic bondingproperties. As a result, the film became a high dielectric.

As described above, leakage characteristics can be improved withoutcausing remanent polarization of conventional ferroelectrics to bechanged by replacing the A site ion of the perovskite orpseudo-perovskite crystal by Si or Ge. Moreover, the film can be used asa high dielectric by eliminating only the remanent polarization whilemaintaining the relative dielectric constant. Therefore, functionaldesign of ferroelectrics can be easily achieved by using theferroelectric film of the present embodiment.

3. First Ferroelectric Memory

A ferroelectric memory including a capacitor which includes theferroelectric film according to the embodiment of the present inventionis described below in detail.

FIG. 12 is a cross-sectional view schematically showing a firstferroelectric memory 1000. The first ferroelectric memory 1000 includesa transistor formation region for controlling the ferroelectric memory.The transistor formation region corresponds to a substrate 100.

The substrate 100 includes a transistor 12 formed on a semiconductorsubstrate 10. A conventional configuration may be applied to thetransistor 12. A film transistor (TFT) or MOSFET may be used as thetransistor 12. In the example shown in FIG. 12, a MOSFET is used as thetransistor 12, and the transistor 12 includes drain/sources 14 and 16and a gate electrode 18.

An electrode 15 is formed on the drain/source 14, and a plug electrode26 is formed on the drain/source 16. The plug electrode 26 is connectedwith a first electrode 20 of a ferroelectric capacitor C100 through abarrier layer, if necessary. The memory cells are separated by anelement isolation region 17 such as LOCOS or trench isolation. Aninterlayer dielectric 19 is formed of an insulator such as silicon oxideon the semiconductor substrate 10 on which the transistor 12 and thelike are formed.

In the above-described configuration, the structure under theferroelectric capacitor C100 forms the transistor formation region whichis the substrate 100. In more detail, the transistor formation region isformed of a structure including the transistor 12, the electrodes 15 and26, and the interlayer dielectric 19 formed on the semiconductorsubstrate 10. The ferroelectric capacitor C100 manufactured by using themanufacturing method of the present embodiment is formed on thesubstrate 100.

The ferroelectric memory 1000 has a structure of storing charge as datain a storage capacitor in the same manner as the DRAM cell.Specifically, the memory cell includes the transistor and theferroelectric capacitor, as shown in FIGS. 13 and 14.

FIG. 13 shows a 1T1C cell type ferroelectric memory in which the memorycell includes one transistor 12 and one ferroelectric capacitor C100.The memory cell is located at an intersecting point of a wordline WL anda bitline BL. One end of the ferroelectric capacitor C100 is connectedwith the bitline BL through the transistor 12 which connects ordisconnects the ferroelectric capacitor C100 and the bitline BL. Theother end of the ferroelectric capacitor C 100 is connected with a plateline PL. A gate of the transistor 12 is connected with the wordline WL.The bitline BL is connected with a sense amplifier 200 which amplifies asignal charge.

An example of the operation of the 1T1C cell is described below briefly.

In the read operation, the bitline BL is set at 0 V, and the transistor12 is turned ON by applying voltage to the wordline WL. The amount ofpolarization charge corresponding to data stored in the ferroelectriccapacitor C100 is transmitted to the bitline BL by increasing voltageapplied to the plate line PL from 0 V to about a power supply voltageV_(CC). The stored data can be read as V_(CC) or 0 V by amplifying asmall potential change generated by the amount of polarization charge byusing the differential sense amplifier 200.

In the write operation, the transistor 12 is turned ON by applyingvoltage to the wordline WL, and the polarization state of theferroelectric capacitor C100 is changed by applying voltage between thebitline BL and the plate line PL.

FIG. 14 shows a 2T2C cell type ferroelectric memory in which the memorycell includes two transistors 12 and two ferroelectric capacitors C100.The 2T2C cell has a structure of retaining complementary data bycombining two 1T1C cells described above. Specifically, in the 2T2Ccell, data is detected by inputting complementary signals to the senseamplifier 200 from two memory cells, in which data has beencomplementarily written, as two differential inputs. Therefore, sincethe data is written in two ferroelectric capacitors C100 in the 2T2Ccell the same number of times, the deterioration state of theferroelectric films of the ferroelectric capacitors C100 becomes equal,whereby a stable operation can be achieved.

2. Second Ferroelectric Memory

FIGS. 15 and 16 show a ferroelectric memory 2000 including MIStransistor type memory cells. The ferroelectric memory 2000 has astructure in which the ferroelectric capacitor C100 is directlyconnected to a gate insulating layer 13. In more detail, thesource/drains 14 and 16 are formed in the semiconductor substrate 10,and the ferroelectric capacitor C100, in which the floating gateelectrode (first electrode) 20, the ferroelectric film 40 according tothe present invention, and the gate electrode (second electrode) 50 arestacked, is connected to the gate insulating layer 13. As theferroelectric film 40, a ferroelectric film formed by applying themanufacturing method of the above embodiment is used. In theferroelectric memory 2000, the semiconductor substrate 10, thesource/drains 14 and 16, and the gate insulating layer 13 correspond tothe substrate 100.

In the ferroelectric memory 2000, the wordline WL is connected with thegate electrode 50 of each cell, and the drain is connected with thebitline BL, as shown in FIG. 16. In this ferroelectric memory, the datawrite operation is performed by applying an electric field between thewordline WL and the well (source) of the selected cell. The readoperation is performed by selecting the wordline WL corresponding to theselected cell, and detecting the amount of current flowing through thetransistor using the sense amplifier 200 connected with the bitline BLof the selected cell.

5. Third Ferroelectric Memory

FIG. 17 schematically shows a third ferroelectric memory. FIG. 18 is anenlarged plan view showing a part of a memory cell array. FIG. 19 is across-sectional view taken along the line 19-19 of FIG. 18. In the planview, numbers in parentheses indicate layers under the uppermost layer.

As shown in FIG. 17, a ferroelectric memory device 3000 in this exampleincludes a memory cell array 100A in which memory cells 120 are arrangedin the shape of a simple matrix, and various circuits for selectivelywriting or reading data in or from the memory cell 120 (ferroelectriccapacitor C100), such as a first driver circuit 150 for selectivelycontrolling the first signal electrode (first electrode) 20, a seconddriver circuit 152 for selectively controlling the second signalelectrode (second electrode) 50, and a signal detection circuit such asa sense amplifier (not shown).

In the memory cell array 100A, the first signal electrodes (wordlines)20 for selecting the row and the second signal electrodes (bitlines) 50for selecting the column are arranged to intersect at right angles.Specifically, the first signal electrodes 20 are arranged at a specificpitch along the X direction. The second signal electrodes 50 arearranged at a specific pitch along the Y direction which intersects theX direction at right angles. The configuration of the signal electrodesmay be the reverse of the above-described configuration. The firstsignal electrode may be the bitline and the second signal electrode maybe the wordline.

In the memory cell array 100A according to the present embodiment, thefirst signal electrode 20, the ferroelectric film 40 according to thepresent invention, and the second signal electrode 50 are stacked on theinsulating substrate 100, as shown in FIGS. 18 and 19. The first signalelectrode 20, the ferroelectric layer 30 formed by applying themanufacturing method of the present embodiment, and the second signalelectrode 50 make up the ferroelectric capacitor 120. Specifically, amemory cell including the ferroelectric capacitor 120 is formed in theintersecting region of the first signal electrode 20 and the secondsignal electrode 50.

A dielectric layer 38 is formed between laminates consisting of theferroelectric film 40 and the second signal electrode 50 so as to coverexposed surfaces of the substrate 100 and the first signal electrode 20.The dielectric layer 38 preferably has a dielectric constant lower thanthe dielectric constant of the ferroelectric film 40. The floatingcapacitance of the first and second signal electrodes 20 and 50 can bereduced by allowing the dielectric layer 38 having a dielectric constantlower than that of the ferroelectric film 40 to be formed between thelaminates consisting of the ferroelectric film 40 and the second signalelectrode 50. As a result, the read and write operations of theferroelectric memory 3000 can be performed at a higher speed.

An example of the read and write operations of the ferroelectric memory3000 is described below.

In the read operation, a read voltage V₀ is applied to the capacitor inthe selected cell. This also serves as a write operation of “0”. At thistime, current flowing through the selected bitline or a potential whencausing the bitline to be in a high impedance state is read by using thesense amplifier. A given voltage is applied to the capacitors in theunselected cells in order to prevent occurrence of crosstalk duringreading.

In the write operation of “1”, a voltage −V₀ is applied to the capacitorin the selected cell. In the case of writing “0”, a voltage which doesnot cause polarization reversal of the selected cell is applied to thecapacitor in the selected cell, thereby retaining the “0” state writtenduring the read operation. A given voltage is applied to the capacitorsin the unselected cells in order to prevent occurrence of crosstalkduring writing.

The above-described ferroelectric memory includes a ferroelectriccapacitor including a ferroelectric film having excellent hysteresischaracteristics with high insulating properties. Therefore, the presentembodiment can provide a highly reliable ferroelectric memory.

Examples of the storage capacitance type, MIS transistor type, andsimple matrix type ferroelectric memories are described above. However,the ferroelectric memory of the present invention is not limitedthereto. The ferroelectric memory of the present invention may beapplied to other types of memory transistors.

6. Piezoelectric Device and Ink-Jet Recording Head

A piezoelectric device and an ink-jet recording head in the embodimentof the present invention are described below in detail.

As an ink-jet recording head in which a part of a pressure generatingchamber connected with a nozzle orifice from which an ink droplet isejected is formed by using a diaphragm, and the ink droplet is ejectedfrom the nozzle orifice by pressurizing the ink in the pressuregenerating chamber by deforming the diaphragm using a piezoelectricdevice, an ink-jet recording head using a longitudinal vibration modepiezoelectric actuator which expands and contracts in the axialdirection of the piezoelectric device, and an ink-jet recording headusing a flexural vibration mode piezoelectric actuator have been putinto practical use.

As an ink-jet recording head using the flexural vibration mode actuator,an ink-jet recording head obtained by forming a uniform piezoelectriclayer over the entire surface of the diaphragm by using a depositiontechnology, and cutting the piezoelectric layer into a shapecorresponding to the pressure generating chamber by using a lithographicmethod so that the piezoelectric device is independently formed in unitsof the pressure generating chambers has been known.

FIG. 20 is an exploded perspective view schematically showing an ink-jetrecording head according to one embodiment of the present invention.FIG. 21A is a plan view of FIG. 20. FIG. 21B is a cross-sectional viewof FIG. 21A. FIG. 22 is a cross-sectional view showing a piezoelectricdevice 3000. As shown in the drawings, a channel forming substrate 110is formed of a (110)-oriented silicon single crystal substrate, and anelastic film 50 with a thickness of 1 to 2 μm, which is made of silicondioxide formed in advance by using thermal oxidation, is formed on oneside of the channel forming substrate 10. A plurality of pressuregenerating chambers 112 are disposed in the channel forming substrate110 in parallel in the widthwise direction. A communication section 113is formed in the channel forming substrate 110 in the region outside thepressure generating chamber 112 in the longitudinal direction of thepressure generating chamber 112. The communication section 113 isconnected with the pressure generating chambers 112 through ink supplypaths 114 provided in units of the pressure generating chambers 112. Thecommunication section 113 is connected with a reservoir section 320 of asealing substrate 300 described later to make up a part of a reservoir102 as a common ink chamber for the pressure generating chambers 112.The ink supply path 114 is formed to have a width smaller than the widthof the pressure generating chamber 112, and maintains channel resistanceof the ink, which flows into the pressure generating chamber 112 fromthe communication section 113, constant.

A nozzle plate 220, in which nozzle orifices 221 connected with thepressure generating chambers 112 near the edge opposite to the inksupply path 114 are formed, is secured to the channel forming substrate110 on the opening side through an adhesive, a thermal-deposited film,or the like.

The elastic film 500 with a thickness of about 1.0 μm is formed on thechannel forming substrate 110 on the side opposite to the opening sideas described above. An insulator film 550 with a thickness of about 0.4μm is formed on the elastic film 500. A lower electrode film 600 with athickness of about 0.2 μm, a piezoelectric layer 700 with a thickness ofabout 1.0 μm, and an upper electrode film 800 with a thickness of about0.05 μm are stacked on the insulator film 550 using a process describedlater to make up the piezoelectric device 3000. The piezoelectric device3000 is the section including the lower electrode film 600, thepiezoelectric layer 700, and the upper electrode film 800. Generally,one of the electrodes of the piezoelectric device 3000 is used as acommon electrode, and the other electrode and the piezoelectric layer700 are patterned in units of the pressure generating chambers 112. Asection which is formed by the patterned electrode and piezoelectriclayer 700 and in which a piezoelectric strain occurs by applying avoltage between the electrodes is called a piezoelectric active section.In the present embodiment, the lower electrode film 600 is used as thecommon electrode for the piezoelectric devices 3000, and the upperelectrode film 800 is used as the individual electrodes for thepiezoelectric devices 3000. However, the electrode configuration may bethe reverse of the above electrode configuration depending on a drivercircuit or interconnects. In either case, the piezoelectric activesections are formed in units of the pressure generating chambers. Thepiezoelectric device 3000 and the diaphragm which is displaced due todrive of the piezoelectric device 3000 are collectively called apiezoelectric actuator. The piezoelectric layers 700 are independentlyprovided in units of the pressure generating chambers 112. As shown inFIG. 22, the piezoelectric layer 700 is made up of a plurality offerroelectric film layers 710 (710 a to 710 f).

The ink-jet recording head makes up a part of a recording head unitincluding an ink channel which is connected with an ink cartridge or thelike, and is provided in an ink-jet recording device. FIG. 23schematically shows an example of the ink-jet recording device. As shownin FIG. 23, cartridges 2A and 2B which make up ink supply means areremovably provided to recording head units 1A and 1B, each including theink-jet recording head. A carriage 3 provided with the recording headunits 1A and 1B is provided to a carriage shaft 5 attached to a devicebody 4 so as to be able to move freely in the axial direction. Therecording head units 1A and 1B respectively eject a black inkcomposition and a color ink composition, for example. The driving forceof a drive motor 6 is transferred to the carriage 3 through a pluralityof gear wheels (not shown) and a timing belt 7, whereby the carriage 3carrying the recording head units 1A and 1B is moved along the carriageshaft 5. A platen 8 is provided in the device body 4 along the carriageshaft 5. A recording sheet S as a recording medium such as paper fed byusing a paper feed roller (not shown) or the like is transferred ontothe platen 8.

The above description illustrates the ink-jet recording head whichejects the ink as a liquid jet head as an example. However, the presentinvention aims at a liquid jet head using a piezoelectric device and aliquid jet device in general. As the liquid jet head, a recording headused for an image recording device such as a printer, a color materialjet head used for manufacturing a color filter for a liquid crystaldisplay or the like, an electrode material jet head used for forming anelectrode of an organic EL display, a field emission display (FED), orthe like, a bio-organic substance jet head used for manufacturing abio-chip, and the like can be given.

Since the piezoelectric device of the present embodiment uses the PZTNfilm according to the above embodiment as the piezoelectric layer, thefollowing effects are obtained.

(1) Since covalent bonding properties in the piezoelectric layer areincreased, the piezoelectric constant can be increased.

(2) Since vacancies of PbO in the piezoelectric layer can be reduced,occurrence of a heterophase at the interface between the piezoelectriclayer and the electrode is prevented, whereby an electric field iseasily applied. Therefore, efficiency of the piezoelectric device can beincreased.

(3) Since a current leakage from the piezoelectric layer is reduced, thethickness of the piezoelectric layer can be reduced.

Since the liquid jet head and the liquid jet device of the presentembodiment utilize the piezoelectric device including the abovepiezoelectric layer, the following effect is obtained.

(4) Since fatigue deterioration of the piezoelectric layer can bereduced, a change in the amount of displacement of the piezoelectriclayer over time can be reduced, whereby reliability can be improved.

Examples of a piezoelectric device and an ink-jet recording head aredescribed above. The ferroelectric film of the present invention mayalso be applied to a pyroelectric sensor and a bimorph piezo actuator.

1. A method of manufacturing a ferroelectric film including Pb(Zr,Ti)O₃,the method comprising: using a sol-gel solution for forming Pb(Zr,Ti)O₃which includes at least four-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pbsite ion in an amount of 1% or more.
 2. A method of manufacturing aferroelectric film including Pb(Zr,Ti)O₃, the method comprising: using asol-gel solution for forming Pb(Zr,Ti)O₃ which includes at leastfour-fold coordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amount of 1%or more, wherein a mixed solution prepared by mixing a sol-gel solutionfor forming PbZrO₃ which includes at least four-fold coordinated Si⁴⁺ orGe⁴⁺ in the Pb site ion in an amount of 1% or more with a sol-gelsolution for forming PbTiO₃ which includes at least four-foldcoordinated Si⁴⁺ or Ge⁴⁺ in the Pb site ion in an amount of 1% or moreis used as the sol-gel solution for forming Pb(Zr,Ti)O₃.
 3. A method ofmanufacturing a ferroelectric film including Pb(Zr,Ti)O₃, the methodcomprising: using a sol-gel solution for forming Pb(Zr,Ti)O₃ in whichthe amount of Pb ranges from 90 to 120% of the stoichiometriccomposition of Pb(Zr,Ti)O₃.
 4. A method of manufacturing a ferroelectricfilm including Bi₄Ti₃O₁₂, the method comprising: using a sol-gelsolution for forming Bi₄Ti₃O₁₂ which includes at least four-foldcoordinated Si⁴⁺ or Ge⁴⁺ in the Bi site ion in an amount of 1% or more.5. A method of manufacturing a ferroelectric film including Bi₄Ti₃O₁₂,the method comprising: using a mixed solution prepared by mixing asolution prepared by mixing a sol-gel solution for forming Bi₂O₃ with asol-gel solution for forming TiO₂ at a molar ratio of 2:3 with a sol-gelsolution for forming a dielectric shown by X₂SiO₅, X₄Si₃O₁₂, X₂GeO₅, orX₄Ge₃O₁₂ (wherein X represents Bi³⁺, Fe³⁺, Sc³⁺, Y³⁺, La³⁺, Ce³⁺, Pr³⁺,Nd³⁺, Pm³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺, orLu³⁺) so that Si⁴⁺ or Ge⁴⁺ is included in an amount of 1 mol % or more.6. A method of manufacturing a ferroelectric film including Bi₄Ti₃O₁₂,the method comprising: using a sol-gel solution for forming Bi₄Ti₃O₁₂ inwhich an excess amount of Bi ranges from 90 to 120% of thestoichiometric composition of Bi₄Ti₃O₁₂.